Extractables and leachables (E/L). A two minute read.

Extractables and leachables (E/L) have been the prominent subjects over the last decade when discussing the biocompatibility of medical devices. They have stood out like superstar phenomena, presenting both bright spots and shadows. Extractables refer to substances that can be removed from a medical device under laboratory conditions designed to magnify the device's clinical use, while leachables are those substances that could be released from the device in real clinical settings. As an initial approximation, leachables can be considered a subset of extractables. Their significance has been rapidly increasing for various reasons. One of the most crucial reasons is the growing consensus that animal testing might not be suitable for evaluating human endpoints.

Obtaining detailed information on the actual substances released from devices enables toxicologists to conduct more relevant risk assessments. However, for a rigorous assessment, the quality of data from the laboratory must be sufficient. Toxicologists have limited resources to assess unknowns, and while the Threshold of Toxicological Concern (TTC) can be used, its value is relatively low, and regulatory acceptance of reports with unknowns is limited.

Most E/L studies focus solely on "E," indicating intentional exaggeration. Ideally, the entire range of polarity should be covered when extracting a device with solvents, and the extraction kinetics can be increased by raising the temperature up to 50°C. Nevertheless, not all devices can withstand such conditions. If there is documented evidence that the device is compromised by the extraction conditions—for instance, if the solvent dissolves part of it—then there is leeway to maintain such conditions. A damaged device no longer accurately represents what a patient would receive, so not all conditions make sense in the pursuit of exaggeration.

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